1. Field of the Invention
The present invention relates to a luffing angle measurement system.
2. Description of Related Art
Cranes and aerial work platforms use many devices to detect the distance to, the length of and/or the position of an element, such as a boom, forming a portion of the crane or aerial work platform. These devices rely on contact between the device and a portion of the element having its position and/or length detected. Devices which rely on contact, however, have a limited life span because each physical contact serves to wear and degrade the device. Contact devices also fail because of external factors which prohibit the detection of contact. For instance, most contact devices use electrical switches, and ice and freezing rain can prevent such switches from functioning.
Furthermore, most contact devices only provide a discrete measurement. When contact occurs, this contact indicates that, for example, the boom is at a predetermined position or at a predetermined length. Such contact devices can not supply a continuously varying real-time measurement. Contact devices also have slow response times. The boom will no longer be in the predetermined position by the time the detected contact is processed. Accordingly, contact devices include a certain amount of error.
According to one embodiment, the luffing angle measurement system according to the present invention includes a non-contact distance measuring device mounted on the nose section of a first boom. The non-contact distance measuring device measures the distance to a second boom pivotally connected to the first boom. The non-contact distance measuring device is mounted to the nose section such that as the luffing angle between the first and second booms increases, the distance measured by the non-contact distance measuring device also increases. A controller converts the measured distance into a luffing angle.
In another embodiment of the luffing angle measurement system according to the present invention, a non-contact measuring device is mounted on a nose section of a first boom, and transmits electromagnetic energy towards a second boom pivotally connected to the first boom. The non-contact measuring device receives the electromagnetic energy reflected from the second boom, and measures the time delay between transmission of the electromagnetic energy and reception of the reflected electromagnetic energy. The non-contact measuring device is mounted on the nose section such that as the luffing angle between the first and second booms increases, the measured time delay increases. A controller converts the measured time delay into a luffing angle.
Accordingly, the present invention provides a luffing angle measurement system which does not rely on physical contact, and therefore, does not suffer from the problems and disadvantages associated with such contact oriented devices.
Other objects, features, and characteristics of the present invention; methods, operation, and functions of the related elements of the structure; combination of parts; and economies of manufacture will become apparent from the following detailed description of the preferred embodiments and accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures.